Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell, an electrode assembly and a current collecting component, the shell comprises an end wall, and an anti-explosion valve is arranged on the end wall; the electrode assembly is accommodated in the shell, and the electrode assembly comprises a tab facing the end wall; the current collecting component is arranged between the electrode assembly and the end wall and is electrically connected with the tab, at least one weak part is arranged on the current collecting component, the weak part is configured to be broken when the internal pressure of the secondary battery exceeds a threshold value, and at least part of the current collecting component is bent towards the direction far away from the electrode assembly so as to reduce the shielding of the pressure relief area; in the radial direction of the current collecting component, the span of the weak part is a, the minimum central angle alpha covering the weak part is formed by passing through the center of the current collecting component, the radial minimum width of the area, covered by the angle alpha, of the current collecting component is b, and a is larger than or equal to 0.4b and smaller than or equal to 0.9b; the technical problem that discharge of internal substances is blocked by a current collecting component when the secondary battery is subjected to thermal runaway can be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a secondary battery, a battery pack and an electronic device. Background Art

[0002] In the prior art, to ensure normal pressure relief for secondary batteries and reduce the risk of battery explosion, explosion-proof valves are typically constructed on one or both end walls of the housing. When the pressure within the housing exceeds a threshold, the valve opens to discharge the battery's internal contents in the event of thermal runaway. Even if the valve opens successfully in the event of thermal runaway, the current collecting member will still significantly obstruct the discharge of the battery's internal contents, compromising the battery's safety. Utility Model Content

[0003] The utility model provides a secondary battery, a battery pack and an electronic device, which are used to improve the technical problem that the discharge of internal substances of the secondary battery is blocked by a current collecting component when thermal runaway occurs.

[0004] To achieve the above-mentioned objectives and other related objectives, the present invention provides a secondary battery, a battery pack and an electronic device, wherein the secondary battery includes a shell, an electrode assembly and a current collecting member; the shell includes an end wall, on which an explosion-proof valve is provided; the electrode assembly is accommodated in the shell, and the electrode assembly includes a pole ear facing the end wall; the current collecting member is arranged between the electrode assembly and the end wall and is electrically connected to the pole ear, and at least one weak portion is provided on the current collecting member, and the weak portion is configured to break when the internal pressure of the secondary battery exceeds a threshold value, and at least a portion of the current collecting member is bent away from the electrode assembly to reduce obstruction of the pressure relief area; along the radial direction of the current collecting member, the span of the weak portion is a, the minimum central angle α of the current collecting member covering the weak portion is made through the center of the current collecting member, and the radial minimum width of the area of ​​the current collecting member covered by the angle α is b, 0.4b≤a≤0.9b.

[0005] In the above technical solution, the current collecting member is provided with at least one weak portion. The weak portion is configured to rupture when the internal pressure of the secondary battery exceeds a threshold, causing at least a portion of the current collecting member to bend away from the electrode assembly to reduce obstruction of the pressure relief area on the end wall. The radial span of the weak portion in the current collecting member is defined as a, i.e., the distance from the farthest point of the weak portion from the center of the current collecting member to the closest point of the weak portion to the center of the current collecting member. Considering the various shapes of the outer periphery of the current collecting member, a minimum central angle α through the center of the current collecting member that covers the weak portion is further defined as b, i.e., the minimum radial width of the portion of the current collecting member covered by the weak portion is b. Furthermore, a limit of 0.4b≤a≤0.9b is defined. This configuration prevents the weak portion from radially penetrating the current collecting member, which could result in the current collecting member being split into multiple pieces by the weak portion. It also enhances the structural strength of the current collecting member, improves its flatness, reduces the difficulty of welding the current collecting member to the tab, and improves the reliability of the welded connection.

[0006] In an example of the secondary battery of the present invention, along the radial direction of the current collecting member, the maximum distance from the weak portion to the center of the current collecting member is R1, and the minimum distance from the explosion-proof valve to the center of the end wall is R2, wherein R2-R1≤3mm.

[0007] In the above technical solution, R2-R1 is limited to 3mm, that is, the maximum distance between the pressure relief area formed on the current collecting component after the partial current collecting component is folded and the pressure relief area formed on the end wall after the explosion-proof valve is opened is less than or equal to 3mm, so as to achieve the maximum possible fracture and folding of the weak part, so as to further reduce the obstruction to the discharge of internal substances.

[0008] In an example of the secondary battery of the present invention, the current collecting member includes a central hole, and the minimum distance from the weak portion to the edge of the central hole is c, where c≤2 mm.

[0009] In the above technical solution, c≤2mm means that the distance between the position of the weak part closest to the center hole and the center hole is less than or equal to 2mm. This setting is conducive to easy tearing of the end of the weak part close to the center hole during pressure relief, which is conducive to improving the pressure relief effect.

[0010] In an example of the secondary battery of the present invention, R2-R1≥c.

[0011] In the above technical solution, the setting of R2-R1≥c can be understood as limiting the distance between the position closest to the center hole of the weak part and the center hole to be less than or equal to the distance between the position closest to the explosion-proof valve of the weak part and the explosion-proof valve. This setting can ensure the flatness and structural strength of the current collecting component while also making it easier to tear the end of the weak part close to the center hole during pressure relief, so as to form a radial folding effect from the inside to the outside along the current collecting component. This setting is more conducive to improving the pressure relief effect.

[0012] In an example of the secondary battery of the present invention, there are multiple weak parts, and at least one of the multiple weak parts is not connected to the other weak parts.

[0013] In the above technical solution, multiple weak parts are not connected or are less connected, which can prevent the current collecting component from breaking easily at the part where multiple weak parts are connected during transportation or welding. It can also improve the structural strength and surface flatness of the current collecting component, thereby reducing the difficulty of welding the current collecting component and the tab and improving the reliability of the welding connection.

[0014] In an example of the secondary battery of the present invention, there are at least three weak parts, all of which are distributed along the circumference of the current collecting component. The angle of the radial outermost contour of the interval area between each two adjacent weak parts is β, where β≤120°.

[0015] In the above technical solution, the number of weak parts is at least three, which can achieve the purpose of dividing the current collecting component into at least three aforementioned spacing areas along its circumference. The spacing area is the portion between two adjacent weak parts along the circumference of the current collecting component. When the weak part breaks under the action of internal pressure, the spacing area can be folded from the inside to the outside to reduce obstruction of the pressure relief area of ​​the end wall. Compared with the case of one or two weak parts, the number of weak parts is greater than or equal to three, which is more conducive to folding after breaking, and the smaller the angle, the easier the folding. Limiting β to ≤ 120° not only facilitates the folding of the spacing area, but also makes the weak parts more evenly distributed, thereby making the stress on the spacing area more uniform, facilitating the synchronous rupture of the weak parts, and reducing the probability of unsuccessful folding of individual spacing areas.

[0016] In an example of a secondary battery of the present invention, the current collecting member is welded to the shell to form at least one first weld mark. Along the circumference of the current collecting member, two points located on both sides of the first weld mark are respectively connected to the center of the current collecting member to form a central angle γ. The area surrounded by each weak portion or the interval area between each two adjacent weak portions can form a bent portion when the internal pressure of the secondary battery exceeds a threshold value. The minimum central angle δ covering the bent portion is formed through the center of the current collecting member, and each central angle δ at least partially overlaps with the central angle γ.

[0017] In the above technical solution, the area between each two adjacent weak portions can form a bend under the action of an internal pressure exceeding a threshold. Furthermore, when the weak portion is in the shape of a broken line or curve, the area enclosed by the weak portion can also form a bend under the action of an internal pressure exceeding a threshold. Furthermore, by ensuring that each central angle δ and the central angle γ at least partially overlap, it is possible to ensure that when the bend folds outward, at least part of the weld between the current collecting member and the housing can serve as a fulcrum for the bend. This arrangement facilitates smooth folding of the bend and further improves the safety of the secondary battery.

[0018] In an example of the secondary battery of the present invention, the minimum distance between the first weld mark and the weak portion is greater than or equal to 1 mm.

[0019] In the above technical solution, this setting can ensure that the weak part and the first weld mark have a safety distance greater than or equal to 1 mm, which can prevent the current collecting component from having problems such as explosion points and weld penetration during the welding process with the shell, reduce safety hazards, and improve welding quality.

[0020] In an example of the secondary battery of the present invention, the current collecting member is welded to the tab to form at least one second weld mark, and the minimum distance between the second weld mark and the weak portion is greater than or equal to 1 mm.

[0021] In the above technical solution, this setting can ensure that the weak part and the second weld mark have a safety distance greater than or equal to 1 mm, which can prevent the current collecting component from having problems such as explosion points and weld penetration during the welding process with the tab, reduce safety hazards, and improve welding quality.

[0022] The utility model also provides a battery pack, which includes any one of the above-mentioned secondary batteries.

[0023] The utility model also provides an electronic device, which includes the above-mentioned battery pack.

[0024] In the secondary battery of the present invention, a plurality of weak parts are provided on the current collecting member, which are configured to break when the internal pressure of the secondary battery exceeds a threshold value. At least part of the current collecting member is bent away from the electrode assembly to reduce the obstruction of the pressure relief area on the end wall. The distance from the farthest point of the weak part from the center of the current collecting component to the closest point of the weak part from the center of the current collecting component is defined as a, that is, the radial span of the weak part in the current collecting component is a. Taking into account the possibility that the outer periphery of the current collecting component may be of various shapes, the minimum central angle α of the current collecting component covering the weak part is further defined, and the radial minimum width of the area of ​​the current collecting component covered by the angle α is b, that is, the minimum radial width of the entity of the part covered by the weak part on the current collecting component is b, and it is limited to 0.4b≤a≤0.9b. This setting can prevent the weak part from penetrating the current collecting component in the radial direction, affecting the structural strength of the current collecting component, and then causing the current collecting component to be easily cut into multiple independent structures by the weak part during transportation and welding, affecting the overall flatness of the current collecting component. This setting can enhance the structural strength of the current collecting component, make the current collecting component have a higher flatness, reduce the difficulty of welding the current collecting component and the tab, and improve the reliability of the welding connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a schematic diagram of the overall structure of an example of a secondary battery of the present invention;

[0027] Figure 2 This is a schematic diagram of the structure of an electrode assembly of an example of a secondary battery of the present invention;

[0028] Figure 3 This is a schematic diagram of welding the first current collecting member and the electrode assembly of an example of the secondary battery of the present invention;

[0029] Figure 4 This is a schematic diagram of welding the first current collecting member and the electrode assembly of another example of the secondary battery of the present invention;

[0030] Figure 5 A schematic diagram of an example of a battery pack of the present invention;

[0031] Figure 6 FIG. 1 is a schematic diagram of an example of the electronic device of the present invention.

[0032] Component number description

[0033] 1. Electronic device; 10. Battery pack; 11. Working unit; 101. Box; 102. Box cover; 100. Secondary battery; 110. Housing; 111. Second end wall; 112. Side wall; 113. Opening; 114. First end wall; 115. Explosion-proof valve; 120. Electrode assembly; 121. Second pole piece; 1211. Positive electrode current collector; 1212. Second coated area; 1213. Second uncoated area; 12 2. Diaphragm; 123. First electrode sheet; 1231. Negative electrode current collector; 1232. First coated area; 1233. First uncoated area; 124. First electrode tab; 125. Second electrode tab; 126. Winding structure; 130. Electrode column; 140. First current collecting component; 141. Weak portion; 142. First weld mark; 143. Second weld mark; 144. Center hole; 145. Bend portion; 150. Second current collecting component. DETAILED DESCRIPTION

[0034] The following describes the implementation of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation methods. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following examples and the features in the examples can be combined with each other unless there is a conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific implementation methods, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0035] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the endpoints may be used. Unless otherwise defined, all technical and scientific terms used in this utility model are consistent with the prior art as understood by those skilled in the art and the description of this utility model. Any prior art methods, equipment, and materials similar or equivalent to those in the examples of this utility model may also be used to implement this utility model.

[0036] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0037] A secondary battery includes a housing and an electrode assembly. The electrode assembly is housed in the housing and is the component where electrochemical reactions occur in the secondary battery. The housing may contain one or more electrode assemblies.

[0038] An electrode assembly is primarily formed by winding or stacking positive and negative electrode sheets, with a separator typically positioned between them. The positive electrode sheet includes a positive current collector and a positive active material, with the positive active material coated on the surface of the positive current collector. The positive current collector includes a coated area coated with the active material and an uncoated area not coated with the active material. The uncoated area, when wound, forms the positive electrode tab of the electrode assembly. The negative electrode sheet includes a negative current collector and a negative active material, with the negative active material coated on the surface of the negative current collector. The negative current collector includes a coated area coated with the active material and an uncoated area not coated with the active material. The uncoated area, when wound, forms the negative electrode tab of the electrode assembly.

[0039] The secondary battery also includes a current collecting member arranged between the end wall of the shell and the corresponding end face of the electrode assembly. The current collecting member is welded to the positive electrode tab or the negative electrode tab to form a tab connection portion. In addition, an explosion-proof valve is constructed on one or both end walls of the shell so that when the battery suffers thermal runaway, the explosion-proof valve opens to discharge the internal substances of the battery.

[0040] However, the inventors found that when a secondary battery experiences thermal runaway, even if the explosion-proof valve opens smoothly, the current collecting component will still cause a large obstruction to the discharge of internal substances of the secondary battery, which will reduce the safety of the secondary battery. In order to solve this problem, in some current collecting components, the inventors disconnected the adjacent pole ear connecting parts of the current collecting components from each other, which can be folded during pressure relief to reduce the obstruction to the discharge of internal substances. However, this setting will reduce the overall strength of the current collecting component and affect the flatness of the current collecting component, which will increase the difficulty of welding the current collecting component to the pole ear and reduce the reliability of the welding connection between the current collecting component and the pole ear.

[0041] In view of this, the present invention provides a technical solution, in which a plurality of weak portions are provided on the current collecting component, and the weak portions are configured to break when the internal pressure of the secondary battery exceeds a threshold value. At least a portion of the current collecting component is bent in a direction away from the electrode assembly to reduce the obstruction of the pressure relief area on the end wall, so as to improve the technical problem that the discharge of internal substances is blocked by the current collecting component when the secondary battery suffers thermal runaway.

[0042] See also Figures 1 to 6 The present invention provides a secondary battery 100 , which includes a housing 110 , an electrode assembly 120 , a terminal post 130 , and a current collecting member.

[0043] See also Figure 1 The shell 110 includes end walls. Specifically, in this embodiment, the shell 110 includes a first end wall 114 and a second end wall 111 that are opposite to each other, and a side wall 112 surrounding the first end wall 114 and the second end wall 111. In order to ensure normal pressure relief of the secondary battery 100 and reduce the risk of explosion of the secondary battery 100, an explosion-proof valve 115 is usually provided on the first end wall 114 and / or the second end wall 111. The shape of the explosion-proof valve 115 can be circular, petal-shaped, rectangular, elliptical, polygonal or other irregular shapes. The explosion-proof valve 115 can be a closed shape or an open shape. The explosion-proof valve 115 can be a notched or thinned structure, etc. There is no limitation on this. As long as it can be achieved that when the internal pressure of the secondary battery 100 reaches a threshold, the explosion-proof valve 115 can be opened to form a pressure relief area for pressure relief, thereby achieving directional explosion of the secondary battery 100.

[0044] See also Figure 1As long as a stable seal and electrical connection can be formed, the connection between the first end wall 114 and the side wall 112, and between the second end wall 111 and the side wall 112, can be achieved in a variety of ways, such as integral stamping, integral casting, or separate welding. The shape of the side wall 112 is not limited and can be cylindrical or prismatic, or can be formed along any other closed loop profile that matches the first end wall 114 and the second end wall 111. As an example, in this embodiment, the outer edges of the first end wall 114 and the second end wall 111 are circular, and the side wall 112 is cylindrical and surrounds the outer edges of the first end wall 114 and the second end wall 111. The second end wall 111 and the side wall 112 are integrally formed, and a circular opening 113 is formed at the end of the side wall 112 near the first end wall 114. The housing 110 enclosed by the second end wall 111 and the side wall 112 has a receiving cavity formed therein for accommodating the electrode assembly 120, electrolyte, and other necessary battery components. Specifically, the diameter of the housing 110 can be determined according to the specific size of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. The housing 110 can be made of a variety of materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. To prevent the housing 110 from rusting during long-term use, the surface of the housing 110 can be plated with a layer of rust-proof material such as metal nickel.

[0045] See also Figures 1 to 2 The electrode assembly 120 is housed in the housing 110 and includes a tab facing the end wall. Specifically, the electrode assembly 120 is a component where electrochemical reactions occur in the secondary battery 100. The housing 110 may contain one or more electrode assemblies 120. The electrode assembly 120 includes a first electrode sheet 123, a second electrode sheet 121, and a winding structure 126 formed by stacking and winding a separator 122. The polarity of the first electrode sheet 123 is opposite to that of the second electrode sheet 121. In some embodiments, the first electrode sheet 123 is a positive electrode sheet and the second electrode sheet 121 is a negative electrode sheet. In other embodiments, the first electrode sheet 123 is a negative electrode sheet and the second electrode sheet 121 is a positive electrode sheet.

[0046] See also Figures 1 to 2 In this embodiment, the first electrode sheet 123 is a negative electrode sheet, and the first electrode sheet 123 includes a negative electrode current collector 1231 and a negative electrode active material. The negative electrode active material is coated on the surface of the negative electrode current collector 1231; the negative electrode current collector 1231 includes a first coated area 1232 coated with the active material and a first uncoated area 1233 not coated with the active material. The first uncoated area 1233 is located at the end of the first electrode sheet 123. The first uncoated area 1233 extends out of the separator 122 along the winding axis direction of the electrode assembly 120 and is bent toward the winding axis to form a first electrode tab 124. The first electrode tab 124 is the corresponding negative electrode tab.

[0047] See also Figures 1 to 2The second electrode sheet 121 is a positive electrode sheet. Specifically, the second electrode sheet 121 includes a positive electrode current collector 1211 and a positive electrode active material. The positive electrode active material is coated on the surface of the positive electrode current collector 1211; the positive electrode current collector 1211 includes a second coated area 1212 coated with an active material and a second uncoated area 1213 not coated with an active material. The second uncoated area 1213 is located at the end of the second electrode sheet 121. The second uncoated area 1213 extends out of the diaphragm 122 at the other end along the winding axis direction of the electrode assembly 120 and is bent toward the winding axis to form a second electrode tab 125. The second electrode tab 125 is the corresponding positive electrode tab.

[0048] See also Figures 1 to 2 The separator 122 is arranged between the first electrode 121 and the second electrode 123 to separate the positive electrode active material layer from the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1211 can be aluminum, and the positive electrode active material layer includes a positive electrode active material. The positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. The material of the negative electrode current collector 1231 can be copper, and the negative electrode active material layer includes a negative electrode active material. The negative electrode active material can be carbon or silicon, etc. The base material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. In order to protect and insulate the battery cell, an insulating film can also be coated on the outside of the battery cell. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC) or other high molecular polymer materials.

[0049] See also Figure 1 and Figure 2 Furthermore, the first tab 124 faces the first end wall 114 or the second end wall 111, while the second tab 125 faces the other end of the housing 110. In this embodiment, the second tab 125 faces the second end wall 111 and is electrically connected to the pole 130, causing the pole 130 to be positively charged. The first tab 124 faces the first end wall 114, and the housing 110 is electrically connected to the first tab 124, causing the pole 130 to be negatively charged. However, in other embodiments, the first tab 124 may be connected to the pole 130, while the second tab 125 may be connected to the housing 110.

[0050] See also Figure 1 and Figure 2The pole 130 passes through the second end wall 111 and is insulated from the second end wall 111. The structure of the pole 130 can be any suitable form that can pass through the second end wall 111 and electrically connect to the first pole piece 123 or the second pole piece 121. For example, the cross-section can be circular, square, prismatic, or a special-shaped profile that can achieve stable electrical conductivity. The end of the pole 130 facing the electrode assembly 120 passes through the second end wall 111 and is directly electrically connected to the first pole tab 124 or the second pole tab 125 or is electrically connected through an indirect transfer. For example, the pole 130 can be electrically connected to the first pole piece 123 through a current collecting member. The end of the pole 130 facing away from the electrode assembly 120 is exposed to the outside of the shell 110 to form a corresponding electrode. The electrical property of the pole 130 can be positive or negative. For example, in one embodiment, the pole 130 is electrically connected to the first pole piece 123. If the polarity of the first pole piece 123 is positive, the pole 130 is the positive electrode, and the shell 110 forms the corresponding negative electrode. In another embodiment, if the polarity of the first electrode piece 123 is negative, the electrode post 130 is the negative electrode, and the housing 110 forms the corresponding positive electrode. In this embodiment, a mounting hole for the electrode post 130 is provided on the second end wall 111. The electrode post 130 is installed in the mounting hole in a sealed and insulated manner. The electrode post 130 is electrically connected to the second electrode tab 125 via a current collecting member. For ease of distinction and understanding, the current collecting member electrically connected to the second electrode tab 125 is designated as the second current collecting member 150. The end of the electrode post 130 facing away from the electrode assembly 120 is exposed to the outside of the housing 110 and is positively charged. The second current collecting member 150 is connected to the positive electrode tab and is preferably made of aluminum.

[0051] The pole 130 is made of a conductive metal material. The material of the pole 130 can be aluminum. If the material of the pole 130 is aluminum, the riveting process can be easily performed. In this embodiment, the pole 130 is made of aluminum and has a positive polarity. Corresponding to the pole 130, the shell 110 is made of low-carbon steel and forms a negative pole accordingly. The pole 130 is electrically insulated from the shell 110. Electrical insulation between the pole 130 and the second end wall 111 of the shell 110 can be achieved in various ways. For example, insulation can be achieved by placing an insulating gasket between the pole 130 and the second end wall 111. Alternatively, insulation can be achieved by forming an insulating coating layer on a portion of the pole 130. Alternatively, some of the above methods can be applied in combination.

[0052] Further, see Figure 1The electrode assembly 120 is electrically connected to the housing 110 via a current collecting member. Specifically, the current collecting member is welded to the first electrode tab 124. For ease of distinction and understanding, the current collecting member electrically connected to the first electrode tab 124 is referred to as the first current collecting member 140. Welding methods such as ultrasonic welding, resistance welding, and laser welding are not limited to this. In this embodiment, laser welding is used. The first current collecting member 140 is connected to the negative electrode tab, and copper is preferably selected as the material. It should be noted that the shapes of the first and second current collecting members 140 and 150 can be any rotationally symmetrical shapes, such as circular, square, regular polygonal, petal-shaped, or other shapes with a center of symmetry that can be aligned with the original shape after being rotated a certain angle around the center of symmetry. This is not limited to this, as long as a stable and reliable electrical connection is achieved. The center of the first and second current collecting members 140 and 150 is their own center of symmetry. In order to improve the positioning, processing convenience, interchangeability and uniformity of the current collecting components during installation, the first current collecting component 140 and the second current collecting component 150 in this embodiment both adopt a circular structure.

[0053] See also Figure 3 and Figure 4 At least one weak portion 141 is provided on the current collecting member, and the weak portion 141 can be provided on the first current collecting member 140 or on the second current collecting member 150, depending on whether the explosion-proof valve 115 is provided on the first end wall 114 or the second end wall 111. In some embodiments, the explosion-proof valve 115 is provided on the first end wall 114, and the weak portion 141 is provided on the first current collecting member 140. In other embodiments, the explosion-proof valve 115 is provided on the second end wall 111, and the weak portion 141 is provided on the second current collecting member 150. In some embodiments, the explosion-proof valve 115 is provided on both the first end wall 114 and the second end wall 111, and the weak portion 141 is provided in both the first current collecting member 140 and the second current collecting member 150. There is no limit to the number of weak portions 141, which may be 1, 2, 3, 4, 5, 6, 7, 8, 9 or more. The shape of the weak portion 141 may be a variety of shapes, such as a straight line, a curve (a wavy line, an arc line, a sine curve, etc.), a broken line, other irregular shapes or a combination of the above. In addition, the structure of the weak portion 141 may be a notch, a thinning, a hollowing or a combination of two or more of the above forms. There is no limit to the above. As long as the weak portion 141 of the secondary battery 100 breaks when the internal pressure of the secondary battery 100 exceeds the threshold, at least part of the current collecting component bends away from the electrode assembly 120 to reduce the obstruction of the pressure relief area on the adjacent first end wall 114 or the second end wall 111, so that the material inside the secondary battery 100 is discharged smoothly, thereby realizing the directional explosion of the secondary battery 100.

[0054] Further, see Figure 3 and Figure 4 , along the radial direction of the first current collecting member 140, the distance from the farthest point of the weak portion 141 from the center of the first current collecting member 140 to the closest point of the weak portion 141 from the center of the first current collecting member 140 is defined as a, that is, the span of the weak portion 141 in the radial direction of the first current collecting member 140 is a, considering that the periphery of the first current collecting member 140 may be of various shapes, further define the minimum central angle α of the center of the first current collecting member 140 covering the weak portion 141, the radial minimum width of the area of ​​the first current collecting member 140 covered by the angle α is b, that is, the first The minimum radial width of the entity of the portion of a current collecting component 140 covered by the weak portion 141 is b, and is limited to 0.4b≤a≤0.9b, for example, it can be 0.4b, 0.5b, 0.6b, 0.7b, 0.8b or 0.9b. This setting can prevent the weak portion 141 from radially penetrating the current collecting component, causing the current collecting component to be cut into multiple pieces by the weak portion 141. At the same time, it can also enhance the structural strength of the current collecting component, improve the flatness of the current collecting component, reduce the difficulty of welding the current collecting component and the tab, and improve the reliability of the welding connection.

[0055] See also Figure 3 and Figure 4 In an example of the secondary battery 100 of the present invention, an explosion-proof valve 115 is provided on the first end wall 114, and a weak portion 141 is provided on the first current collecting member 140. In the radial direction of the first current collecting member 140, the maximum distance from the weak portion 141 to the center of the first current collecting member 140 is R1, and the minimum distance from the explosion-proof valve 115 to the center of the first end wall 114 is R2. R2-R1 is limited to 3mm, that is, the pressure relief area formed on the first current collecting member 140 after the first current collecting member 140 is partially folded is limited to the distance from the explosion-proof valve 115 to the center of the first end wall 114. The maximum distance of the pressure relief area formed on the end wall after the explosion valve 115 is opened is less than or equal to 3mm. R2 can be greater than R1 or less than or equal to R1. When R2>R1, the value of R2-R1 can be 1mm, 1.5mm, 2mm, 2.5mm or 3mm, etc. When R2≤R1, the value of R2-R1 can be -3mm, -2mm, -1mm, 0mm, etc. The above settings can achieve a maximum degree of folding after the weak part 141 breaks, so as to further reduce the obstruction caused by the discharge of internal substances. It should be noted that Figure 3 and Figure 4 The explosion-proof valve 115 shown in the figure is actually located on the first end wall 114. In order to conveniently reflect the positional relationship between the explosion-proof valve 115 and the weak portion 141, the explosion-proof valve 115 is projected onto the current collecting component. In addition, in this embodiment, the first end wall 114 and the current collecting component are coaxially arranged.

[0056] See also Figure 3 and Figure 4In an example of the secondary battery 100 of the present invention, the first current collecting member 140 includes a central hole 144, and the minimum distance from the weak portion 141 to the edge of the central hole 144 is c. Preferably, c≤2mm, for example, it can be 0.2mm, 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm or 2mm, etc. c≤2mm means that the distance between the position closest to the weak portion 141 and the central hole 144 is less than or equal to 2mm. This setting is conducive to easy tearing of the end of the weak portion 141 close to the central hole 144 during pressure relief, which is conducive to improving the pressure relief effect.

[0057] See also Figure 3 and Figure 4 In one example of the secondary battery 100 of the present invention, preferably, R2 - R1 ≥ c. Since c is a variable greater than 0, R2 - R1 indicates that R1 < R2. This arrangement can provide first current collecting member 140 with high structural strength and flatness. Furthermore, the arrangement of R2 - R1 ≥ c can be understood as limiting the distance between the position of weak portion 141 closest to center hole 144 and center hole 144 to be less than or equal to the distance between the position of weak portion 141 closest to explosion-proof valve 115 and explosion-proof valve 115. The specific value of R2 - R1 depends on the value of c. This arrangement ensures the flatness and structural strength of the current collecting member while also making it easier for the end of weak portion 141 closest to center hole 144 to tear during pressure relief, creating a radially inward-to-outward folding effect along the current collecting member. This arrangement further enhances pressure relief.

[0058] See also Figure 3 and Figure 4 In one example of the secondary battery 100 of the present invention, at least one of the multiple weak parts 141 is not connected to the other weak parts 141. Setting multiple weak parts 141 to be non-connected or less connected can prevent the first current collecting member 140 from easily breaking at the part where the multiple weak parts 141 are connected during transportation or welding. It can also improve the structural strength and surface flatness of the first current collecting member 140, thereby reducing the difficulty of welding the first current collecting member 140 to the tab and improving the reliability of the welded connection. In one embodiment, please refer to the figure, multiple weak parts 141 along the circumference of the first current collecting member 140 are not connected to each other,

[0059] See also Figure 3 and Figure 4In an example of the secondary battery 100 of the present invention, multiple weak portions 141 are distributed along the circumference of the first current collecting member 140. The number of weak portions 141 is at least 3, for example, it can be 3, 4, 5, 6, 7, 8, 9 or more. The angle of the radial outermost contour of the spacing area between each two adjacent weak portions 141 is β. It should be noted that the spacing area is the part between two adjacent weak portions 141 along the circumference of the first current collecting member 140. The angle β is ≤ 120°, for example, it can be 30°, 45°, 60°, 75°, 90°, 100°, 115° or 120°, etc. There are at least three weak portions 141, which can divide the first current collecting member 140 into at least three aforementioned spaced regions along its circumference. When the weak portion 141 ruptures under internal pressure, the spaced regions can fold outward from the inside to reduce obstruction of the pressure relief area of ​​the end wall. Compared to one or two weak portions 141, having three or more weak portions 141 facilitates folding after rupture, and the smaller the angle β, the easier the folding. Limiting β to 120° not only facilitates folding of the spaced regions, but also ensures a more even distribution of the weak portions 141, thereby ensuring more uniform stress on the spaced regions. This facilitates the synchronization of the rupture of the weak portions 141 and reduces the probability of unsuccessful folding of individual spaced regions.

[0060] See also Figure 3 and Figure 4 In an example of the secondary battery 100 of the present invention, the first current collecting member 140 is welded to the shell 110 to form at least one first weld mark 142. Along the circumference of the first current collecting member 140, two points on both sides of the first weld mark 142 are connected to the center of the first current collecting member 140 to form a central angle γ. The area surrounded by each weak portion 141 or the interval area between each two adjacent weak portions 141 can form a bending portion 145 when the internal pressure of the secondary battery 100 exceeds the threshold. It should be noted that when the weak portion 141 is Figure 3 When the weak portion 141 is straight, the interval area between each two adjacent weak portions 141 can form a bent portion 145 under the action of an internal pressure exceeding a threshold value; when the weak portion 141 is Figure 4 In the case of the broken line shown, the area enclosed by the weak portion 141 itself can also form a bent portion 145 under the action of an internal pressure exceeding a threshold. Furthermore, a minimum central angle δ is defined through the center of the first current collecting member 140 to cover the bent portion 145. Preferably, each central angle δ is limited to at least partially overlap with the central angle γ. This arrangement allows the bent portion 145 to fold outward, with at least a portion of the weld between the first current collecting member 140 and the housing 110 serving as a fulcrum for the folding of the bent portion 145. This arrangement facilitates the smooth folding of the bent portion 145, further improving the safety of the secondary battery 100.

[0061] See also Figure 3 and Figure 4 In one example of the secondary battery 100 of the present invention, the minimum distance between the first weld mark 142 and the weak portion 141 is greater than or equal to 1 mm. Figure 3 and Figure 4 The marked W1 in the figure indicates that the thickness may be, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or 4 mm. This arrangement allows a safe distance of 1 mm or more between the weak portion 141 and the first weld mark 142, thereby preventing problems such as cracking and weld penetration during welding of the first current collecting member 140 to the housing 110, reducing safety hazards and improving welding quality.

[0062] See also Figure 3 and Figure 4 In an example of the secondary battery 100 of the present invention, the first current collecting member 140 is welded to the tab to form at least one second weld mark 143. The minimum distance between the second weld mark 143 and the weak portion 141 is greater than or equal to 1 mm. Figure 3 and Figure 4 The marked W2 in the figure indicates that the distance may be, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or 4 mm. This arrangement allows a safe distance of 1 mm or more between the weak portion 141 and the second weld mark 143, thereby preventing problems such as explosion spots and weld penetration during welding of the first current collecting member 140 to the tab, reducing safety hazards and improving welding quality.

[0063] It should be noted that the above technical solution is also applicable to the case where the explosion-proof valve 115 is provided on the second end wall 111, and the weak portion 141 is provided on the second current collecting member 150. The specific structure will not be repeated here. This technical solution is only applied to the first current collecting member 140, only to the second current collecting member 150, or when the above two are used at the same time, and it can reduce the effect of blocking the pressure relief area and improve the safety performance of the secondary battery 100.

[0064] In an example of the secondary battery 100 of the present invention, please refer to Figure 3 The weak portion 141 is a linear notch. There are four weak portions 141 evenly distributed along the circumference of the first current collecting component 140. The four weak portions 141 are not connected to each other. a=12.8mm, b=18.2mm, R1=17.7mm, R2=20.2mm, R2-R1=2.5mm, c=0.9mm, β=90°, the central angles γ and δ overlap, w1=12mm, w2=3.6mm.

[0065] In another example of the secondary battery 100 of the present invention, please refer to Figure 4The weak portion 141 is a broken line notch with an included angle of 90°. The corner of the broken line is close to the center of the first current collecting member 140. The opening 113 faces the outer periphery of the first current collecting member 140. Four weak portions 141 are evenly distributed along the circumference of the first current collecting member 140. The four weak portions 141 are not connected to each other. a=14.2mm, b=18.25mm, R1=18mm, R2=20.2mm, R2-R1=2.2mm, c=0.25mm, β=18.5°, the central angles γ and δ overlap, w1=8.6mm, w2=0.65mm.

[0066] The weak portion 141 provided in the above two embodiments can reduce the shielding effect of the first current collecting member 140 on the pressure relief area on the first end wall 114 when thermal runaway of the secondary battery 100 occurs. The technical solutions of the above embodiments are also applicable to the second current collecting member 150 and the second end wall 111, and can achieve the same effect, so this will not be repeated here.

[0067] See also Figure 5 The present invention further provides a battery pack 10, which includes any of the aforementioned secondary batteries 100. In one embodiment of the present invention's battery pack 10, the battery pack 10 includes a housing 101, a housing cover 102, and a plurality of secondary batteries 100. The plurality of secondary batteries 100 are placed in the housing 101 and are connected in series or in parallel, or in a combination of series and parallel. The housing cover 102 seals the housing 101 to protect the plurality of secondary batteries 100. It should be noted that, in addition to the present invention's secondary batteries 100, the battery pack 10 may also include a battery pack 10 thermal management system, a circuit board, and other components. The battery pack 10 may be a battery module, a battery pack, an energy storage cabinet, or the like; these will not be described in detail here.

[0068] See also Figure 6The present invention also provides an electronic device 1, which includes the above-mentioned battery pack 10. The working part 11 is electrically connected to the battery pack 10 to obtain electrical energy support. As an example, the electronic device 1 is a vehicle, and the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited to this. The working part 11 is the vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides electrical energy support for the driving of the vehicle or the operation of electrical components in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. Spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.; the working part 11 can be a unit component that can obtain electrical energy from the battery pack 10 and perform corresponding work, such as a fan blade rotation unit, a vacuum cleaner suction unit, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present embodiment does not impose any particular restrictions on the electronic device 1.

[0069] The secondary battery of the present invention features multiple weak points on the current collecting member. These weak points are configured to rupture when the internal pressure of the secondary battery exceeds a threshold, causing at least a portion of the current collecting member to bend away from the electrode assembly to minimize obstruction of the pressure relief area on the end wall. The distance a is defined from the farthest point of the weak point from the center of the current collecting member to the closest point to the center of the weak point. Furthermore, the minimum central angle α through the center of the current collecting member that covers the weak point is defined as b. The minimum radial width of the area of ​​the current collecting member covered by the angle α is defined as 0.4b≤a≤0.9b. This configuration prevents the weak points from radially penetrating the current collecting member, enhances the structural strength of the current collecting member, ensures a high degree of flatness, reduces the difficulty of welding the current collecting member to the tab, and improves the reliability of the welded connection. Therefore, the present invention effectively overcomes several practical problems of the prior art, thus possessing high utility value and practical significance. The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by persons skilled in the art without departing from the spirit and technical concept disclosed in this utility model shall be covered by the claims of this utility model.

Claims

1. A secondary battery, characterized in that: include: The housing comprises an end wall, wherein the end wall is provided with an explosion-proof valve; an electrode assembly housed in the housing, the electrode assembly comprising a tab facing the end wall; a current collecting member disposed between the electrode assembly and the end wall and electrically connected to the tab, the current collecting member being provided with at least one weak portion configured to break when the internal pressure of the secondary battery exceeds a threshold value, and at least a portion of the current collecting member being bent away from the electrode assembly to reduce obstruction of a pressure relief area; Among them, along the radial direction of the current collecting component, the span of the weak part is a, the minimum central angle α covering the weak part is made through the center of the current collecting component, and the radial minimum width of the area of ​​the current collecting component covered by the angle α is b, 0.4b≤a≤0.9b.

2. The secondary battery according to claim 1, wherein Along the radial direction of the current collecting component, the maximum distance from the weak portion to the center of the current collecting component is R1, and the minimum distance from the explosion-proof valve to the center of the end wall is R2, wherein R2-R1≤3mm.

3. The secondary battery according to claim 2, wherein The current collecting component includes a central hole, and a minimum distance from the weak portion to an edge of the central hole is c, wherein c≤2 mm.

4. The secondary battery according to claim 3, wherein R2-R1≥c.

5. The secondary battery according to claim 1, wherein There are multiple weak parts, and at least one of the multiple weak parts is not connected to the other weak parts.

6. The secondary battery according to claim 1, wherein There are at least three weak parts, all of which are distributed along the circumference of the current collecting component. The rotation angle of the radially outermost contour of the interval area between every two adjacent weak parts is β, where β≤120°.

7. The secondary battery according to claim 6, characterized in that The current collecting member is welded to the shell to form at least one first weld mark. Along the circumference of the current collecting member, two points located on both sides of the first weld mark are respectively connected to the center of the current collecting member to form a central angle γ. When the internal pressure of the secondary battery exceeds a threshold, the area surrounded by each weak portion or the interval area between each two adjacent weak portions forms a bent portion. A minimum central angle δ covering the bent portion is formed through the center of the current collecting member, and each central angle δ at least partially overlaps with the central angle γ.

8. The secondary battery according to claim 7, wherein: The minimum distance between the first weld mark and the weak portion is greater than or equal to 1 mm.

9. The secondary battery according to claim 1, wherein The current collecting member is welded to the tab to form at least one second weld mark, and a minimum distance between the second weld mark and the weak portion is greater than or equal to 1 mm.

10. A battery pack, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 9.

11. An electronic device, characterized in that: A battery pack comprising the battery pack according to claim 10.

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